The current invention generally relates to three-dimensional visual perception technology and more particularly to a system and method for realizing real-time re-focusable stereo vision.
Stereo vision, or stereoscopic vision, better known as 3D vision, realizes three-dimensional visual perception of an object by recording the images of the same object from at least two different viewing angles, and then displaying the two different images separately to each of the two eyes of a viewer. The viewer perception from the separately shown images of the same object to different eyes with different viewing angles is a three-dimensional object existing in the viewer's viewing space.
For motion picture utilizing stereo vision, i.e. 3D movies, image recording by the recording devices generally has only a single focus depth. The objects not being focused upon by the recording devices stay de-focused in the recorded images and are perceived as blurred objects to the viewer during stereoscopic playback of the 3D movies. In prior art practices of 3D recording and viewing, a viewer is not given the ability to re-focus on the defocused and blurred objects as one can do in reality.
For a 3D viewing experience of the viewer to better simulate a real-life three-dimensional visualization of objects within the viewing space of the viewer, it is desirable for a viewer to be able to focus on the objects of interest and be able to re-focus on new objects within the same viewing space, following viewer's own re-focusing intention, for example by viewer's eye-lens change, eyeball position change or brain-wave pattern change that naturally happen during a human vision re-focus event without viewer's active effort to change the focus depth of the shown images. Thus a reality viewing experience can be achieved. The ability of being able to focus on objects of interest by viewer's intention, without active effort from viewer, during stereo vision, gives unprecedented advantage in its closest-to-reality viewing experience. This ability will promote stereo vision's application in areas where varying focus depth vision provides best life-like visual comprehension of an object of interest.
As shown in FIG. 1, vision of a human eye 11 is achieved by three key optical components that determine the imaging of surrounding objects that the eye can see: the Lens (eye-lens) 1, the Retina 2, and the Iris 3. The lens 1 is the component that functions the same as the optical lenses used in cameras. Light reflected or emitted from an outside object passes through the pupil 9 and the lens 1. An optical image of the object is projected on the retina 2 with the light from the object being re-focused by the lens 1. The lens 1 is controlled by the Ciliary Muscle 4 and Ligament 5 which can compress or stretch the lens 1 shape, which in turn changes the optical focus depth of the lens 1 and makes objects at various distances from the viewer producing focused images on the retina 2, and thus the viewer can see objects far or near clearly. This control of lens focus depth gives a viewer the ability to see objects near and far at will. The retina 2 is like a film screen within a camera. When the light from an object passes through the lens land is projected onto the retina 2 and makes a clear and focused image, the vision cells of the retina 2 sense the color and intensity of the projected image and send such information to human brain through the optical nerves 6, and thus human vision is realized. The iris 3 controls the total amount of light that can go into the eye by adjusting the pupil 9 size, which helps maintain the right amount of light intensity that goes into the eye 11 without damaging the retina cells.
FIG. 2 is a schematic diagram illustrating how normal human vision is achieved according to prior art. Same object 29 is projected into different images 25 and 26 in different eyes 21 and 22 of a viewer due to the angle of viewing is different for the two eyes 21 and 22. The angle difference as inferred from the two images 25 and 26 of the same object 29 in the two eyes 21 and 22 as being perceived by the brain is used to extract the information as to how far the object 29 is from the viewer. When images of the same object 29 are taken at different viewing angles, and then projected separately onto the retina 24 of the different eyes 21 and 22 of a viewer, the viewer can also have a similar distance perception of the object in the viewing space, where the object is actually not existent. This gives rise to the stereo vision, or 3D vision, meaning viewing of an object with a distance perception from the viewer.
FIG. 3 is a schematic diagram illustrating stereo-vision being achieved according to prior art. The principle function of all currently existing stereo-vision, or 3D vision, is the same, which includes: (1) Projecting two different images 391 and 392 of the same object 390 (not shown in FIG. 3) captured at two different angles on the same screen 38; (2) Allowing each eye 21 and 22 to see only one of the two images 391 and 392; and (3) The viewer with each eye 21 and 22 seeing a different projected image 25 and 26 from images 391 and 392 taken at different angle of the same object 390 perceives an imaginary object 39 in space that is at a distance from viewer different than the screen 38 where images 391 and 392 are shown.
When the stereo-vision is applied to a motion picture, a 3D movie is produced. The methods used to achieve each eye viewing different images are accomplished by wearing 3D viewing glasses that can do any of: (1) filter polarized light; (2) filter light of different colors; and (3) have timed shutter being synchronized with the showing of different viewing angle images on the screen. By showing the images of the same object recorded at different angles, arranging the images at different locations on the same screen, and using a method to individually show image recorded at different view angle to different eye, viewer perceived an imaginary object in space at a distance from the viewer different than the screen distance to the viewer.
FIG. 4 is a schematic diagram illustrating the problems of the prior art stereo-vision techniques. A fundamental drawback of all existing stereo-vision techniques and 3D movie techniques in the attempt to simulate real-life viewing experience is that when the object images are captured from two different viewing angles, objects 391 and 392 that are focused upon will show up as focused objects when projected on screen. Objects 491 and 492 within the same scene but not focused upon during recording will stay defocused on the screen 38. Thus, when viewer perceived the 3D image, only the objects 391 and 392 that are focused upon during image capturing can be viewed clearly, while other objects 491 and 492 stay blurred. Viewer only sees a clear imaginary object 39 from the images 391 and 392, while object 49 from images 491 and 492 are defocused. The existing prior art techniques do not allow viewer to view all objects within same scene clearly and does not have a method to bring objects into focus at viewer's own discretion. Even though other objects in the recorded images also show up on the same screen 38, due to the fact that the focus was only on the object where images 391 and 392 are taken from, other objects stay defocused. Thus, viewer's intention of focusing upon the objects 491 and 492 that are not currently in-focus cannot be achieved in conventional prior art stereo vision. This limitation makes 3D vision of prior art an obvious deviation from reality. In comparison, in real life, for objects near or far, a viewer can freely adjust to their distance with eye-lens focal length change and eyeball pupil position change and achieve clear view of any object in the viewing angle. Prior art is limited in the ability to re-produce the life-like stereo-vision viewing experience.
It is desired to have a method and an apparatus that can achieve real-time re-focusable vision based on viewer's own re-focus intention to simulate more life-like stereo-vision experience without active viewer participation or intervention.